Single ended sense amplifiers have been used in both embedded and stand alone memory chips, digital signal processors, mixed signal processors, and microprocessors. While slower in speed, they offer lower power and higher noise immunity compared to a differential sense amplifier, and are adapted to requiring only one input data signal.
The configuration and size of transistors in a single-ended sense amplifier circuit are such that a feedback inverter contends with a pre-charge transistor for a substantial period of time during the pre-charge operation. This contention impacts the speed of the sense amplifier circuit by requiring a longer pre-charge period. This impact becomes quite severe when the transistors of the sense amplifier circuit are sized for quicker sensing.
It is therefore desirable to provide a high-speed single ended sense amplifier circuit for use in electronic components.
In accordance with the present invention, an apparatus and method for processing a data input signal with a single ended sense amplifier is provided. The single ended sense amplifier includes a transmission gate circuit and a control circuit coupled between a feedback inverter circuit and an output signal that is fed back to the feedback inverter circuit through said transmission gate. An inverter circuit is coupled between an enable signal and the transmission gate and control circuits. During pre-charge operation, the input to the feedback inverter circuit is driven to a first state, such as high or low. The feedback inverter correspondingly drives the input signal to a sensing inverter to a state that is complementary to the first state, thereby assisting the pre-charge mode and substantially reducing time delay due to the input signal contending with the feedback inverter circuit.
In one embodiment, the single ended sense amplifier circuit includes a pre-charge circuit, and a sensing inverter circuit coupled to receive an input signal charged by the pre-charge circuit. The sensing inverter circuit generates an output signal. A feedback inverter circuit receives the input signal and the output signal, and a transmission gate circuit is coupled between the feedback inverter circuit and the output signal.
One feature of the high-speed single ended sense amplifier circuit is a control circuit coupled to the transmission gate circuit and to the feedback inverter circuit to assist pre-charge of the input through the feedback inverter.
Another feature is an inverter circuit coupled to receive an enable signal. The inverter circuit generates an inverted enable signal to control the transmission gate circuit and drive the control circuit. The control circuit can include a NMOS transistor and the pre-charge circuit can include a PMOS transistor. At the end of pre-charge operation, the enable signal goes high, the control transistor is turned off allowing the input data to flow through the sense amplifier with no contention.
The control circuit can alternatively include a PMOS transistor, and the precharge circuit can include a NMOS transistor. At the end of pre-charge operation, the enable signal goes low, the control transistor is turned off allowing the input data to flow through the sense amplifier with no contention.
A high-speed single ended sense amplifier circuit in accordance with the present invention can be included in a variety of devices, such as a digital signal processor, a memory device, and a mixed signal processing device.
In another embodiment, a method for sensing data input in accordance with the present invention includes:
receiving an input data signal;
receiving an enable signal;
pulling the input data signal to a first state during a pre-charge mode;
inverting the enable signal;
receiving the inverted enable signal in a control circuit; and
pulling a feedback inverter input to a state that is complementary to the first state with an output signal from the control circuit.
The method in accordance with the present invention can further include:
outputting a sense amplifier output signal based on the data input signal;
receiving the enable signal and the inverted enable signal in a transmission gate circuit; and
feeding back the sense amplifier output signal to the feedback inverter through the transmission gate.
One advantage of the present invention is that sense amplifiers can be sized for faster sensing than would other wise be feasible due to the excessive contention during the pre-charge mode.